A5082266055- Solar and Space Plasma Dynamics
- Ionosphere and magnetosphere dynamics
- Astro and Planetary Science
- Geomagnetism and Paleomagnetism Studies
- Stellar, planetary, and galactic studies
- Magnetic confinement fusion research
- Solar Radiation and Photovoltaics
- Radio Astronomy Observations and Technology
- Plasma Diagnostics and Applications
- Astrophysics and Cosmic Phenomena
- Gamma-ray bursts and supernovae
- Geophysics and Gravity Measurements
- Graphite, nuclear technology, radiation studies
- Photovoltaic System Optimization Techniques
- Magnetic Field Sensors Techniques
- Astrophysics and Star Formation Studies
- Cyclone Separators and Fluid Dynamics
- Historical Astronomy and Related Studies
- Fusion materials and technologies
- Solar Thermal and Photovoltaic Systems
- Atomic and Subatomic Physics Research
- Silicon Carbide Semiconductor Technologies
- Electromagnetic Simulation and Numerical Methods
- Laser Design and Applications
- Earthquake Detection and Analysis
University of Manchester
2015-2024
University of Hertfordshire
2023-2024
SKA Observatory
2019
United States Naval Research Laboratory
2013
Culham Centre for Fusion Energy
2013
Culham Science Centre
2013
University of Sheffield
2007-2009
University of Bradford
2004-2006
The observed properties (i.e., source size, position, time duration, decay time) of solar radio emission produced through plasma processes near the local frequency, and hence interpretation bursts, are strongly influenced by propagation effects in inhomogeneous turbulent corona. In this work, a 3D stochastic description process is presented, based on Fokker-Planck Langevin equations radio-wave transport medium containing anisotropic electron density fluctuations. Using numerical treatment...
Abstract Solar radio bursts are strongly affected by radio-wave scattering on density inhomogeneities, changing their observed time characteristics, sizes, and positions. The same turbulence causes angular broadening scintillation of galactic extragalactic compact sources through the solar atmosphere. Using large-scale simulations transport, characteristics anisotropic from 0.1 R ⊙ to 1 au explored. For first time, a profile heliospheric fluctuations is deduced that accounts for properties...
The acceleration of electrons and protons caused by a super-Dreicer electric field directed along the longitudinal component By magnetic is investigated. three-component in nonneutral current sheet occurring at top reconnecting flaring loops on charged particle trajectories energies considered. Particle (RCS) their energy spectra point ejection from RCS are simulated motion equation for different thicknesses. A found to accelerate particles coherent range 10-100 keV 100-400 with slightly...
The effect of a self-induced electric field is investigated analytically and numerically on differential mean electron spectra produced by beam electrons during their precipitation into flaring atmosphere as well the emitted hard X-ray (HXR) photon spectra. induced found to be constant in upper atmospheric layers fall sharply deeper from some "turning point" occurring either corona (for intense softer beams) or chromosphere weaker harder beams). stronger beam, higher before turning point...
Twisted coronal loops should be ubiquitous in the solar corona. magnetic fields contain excess energy, which can released during reconnection, causing flares. The aim of this work is to investigate and particle acceleration transport kink-unstable twisted loops, with a focus on effects resistivity, loop geometry atmospheric stratification. Another perform forward-modelling bremsstrahlung emission determine structure hard X-ray sources. We use combination magnetohydrodynamic (MHD)...
Proton and electron acceleration in a fragmenting periodic current sheet (CS) is investigated, based on the forced magnetic reconnection scenario. The aim to understand role of CS fragmentation high-energy beam generation solar flares. We combine magnetohydrodynamics test-particle models consider particle trajectories consistent with time-dependent model. It shown that accelerated particles such model form two distinct populations. Protons electrons moving open field have energy spectra are...
Photospheric motions may lead to twisted coronal magnetic fields which contain free energy that can be released by reconnection. Browning & Van der Linden suggested such a relaxation event triggered the onset of ideal kink instability. In present work, we study evolution flux tube with zero net axial current following Hood et al. Based on obtained and electric fields, proton electron trajectories are calculated using test-particle approach. We discuss resulting particle distributions...
Electron and proton acceleration by a super-Dreicer electric field is investigated in the non-neutral reconnecting current sheet (RCS) with non-zero longitudinal component of magnetic ('guiding field'). The guiding assumed parallel to direction constant within an RCS. other two components, transverse tangential, are considered vary distances from X null point electron energy spectra calculated numerically motion equation using test particle approach for model RCSs variable densities. In...
<i>Context. <i/>In the present paper, we investigate particle acceleration by direct electric field in solar flares.<i>Aims. <i/>Proton and electron kinetics are considered based on MHD simulations of magnetic reconnection, with aim determining properties accelerated particles a time-dependent reconnecting event model.<i>Methods. <i/>At first, several two-dimensional numerical models forced reconnection initially force-free Harris current sheet. The fields from these were then used to study...
The numerical solutions of the time-dependent kinetic Fokker-Planck equation are presented for fast electrons injected from solar corona into a flaring atmosphere and precipitating with energy pitch-angle diffusion loop converging magnetic field. assumed to lose their in Coulomb collisions particles partially ionised ambient plasma Ohmic heating owing electric field induced by beam. electron beam is found cause return current beam, which comes back source wide pitch angle distribution. arise...
Context. Twisted magnetic fields should be ubiquitous in the solar corona, particularly flare-producing active regions where are strongly non-potential. The energy contained such twisted can released during flares and other explosive phenomena. It has recently been shown that reconnection helical coronal loops results plasma heating particle acceleration distributed within a large volume, including lower chromospheric sections of loops. Hence, scenario involving helicity viable alternative...
In the merging-compression method of plasma start-up, two flux-ropes with parallel toroidal current are formed around in-vessel poloidal field coils, before merging to form a spherical tokamak plasma. This start-up method, used in Mega-Ampere Spherical Tokamak (MAST), is studied as high Lundquist number and low plasma-beta magnetic reconnection experiment. this paper, 2D fluid simulations presented process order understand underlying physics, better interpret experimental data. These examine...
Abstract Low-frequency radio observations make it possible to study the solar corona at distances up 2–3 R ☉ . Frequency of plasma emission is a proxy for electron density emitting and, therefore, bursts can be used probe structure outer corona. In this study, positions sources are investigated using Low-Frequency Array (LOFAR) spectral imaging in frequency range 30–50 MHz. We show that there events where apparent cannot explained standard coronal models. Namely, heliocentric 0.1–0.7 further...
Abstract Recent developments in astronomical radio telescopes opened new opportunities imaging and spectroscopy of solar bursts at subsecond timescales. Imaging narrow frequency bands has revealed temporal variations the positions source sizes that do not fit into standard picture type III bursts, require a better understanding radio-wave transport. In this paper, we utilize 3D Monte Carlo ray-tracing simulations account for anisotropic density turbulence inhomogeneous corona to...
We show how some different fundamental plasma processes - the ideal kink instability, magnetic reconnection and magnetohydrodynamic oscillations can be causally linked. This is shown through revieweing a series of models energy release in twisted flux ropes solar corona, representing confined flares. 3D simulations demonstrate that fragmented current sheets develop during nonlinear phase leading to multiple reconnections stored energy. By coupling these with test particle code, we predict...
Understanding electron acceleration associated with magnetic energy release at sub-second scales presents a major challenges in solar physics. Solar radio spikes observed as sub-second, narrow bandwidth bursts $\Delta{f}/f\sim10^{-3}-10^{-2}$ are indicative of evolution the distribution. We present statistical analysis frequency, and time-resolved imaging individual Type IIIb striae coronal mass ejection (CME). LOFAR reveals that co-temporal ($<2$ s) spike intensity contours almost...
Context . Forced magnetic reconnection, a reconnection event triggered by external perturbation, should be ubiquitous in the solar corona. Energy released during such cases can much greater than that which was introduced perturbation. The exact dynamics of events are determined structure and complexity region: thickness reconnecting layers, field curvature; presence, shapes sizes islands. It is unclear how properties perturbation initial current sheet affect region properties, thereby energy...
The aim of this study is to generate maps the hard X-ray emission produced by energetic electrons in a solar flare and compare them with observations. ultimate goal test viability combined MHD/test-particle approach for data-driven modelling active events corona their impact on heliosphere. Based an MHD model X-class observed 8th September 2017, we calculate trajectories large number protons using relativistic guiding-centre approach. Using obtained particle trajectories, deduce spatial...
Particle acceleration is a fundamental process arising in many astrophysical objects, including active galactic nuclei, black holes, neutron stars, gamma-ray bursts, accretion disks, solar and stellar coronae, planetary magnetospheres. Its ubiquity means energetic particles permeate the Universe influence conditions for emergence continuation of life. In our system, Sun most particle accelerator, its proximity makes it unique laboratory which to explore acceleration. However, despite...
Oscillatory reconnection is a process that has been suggested to underlie several solar and stellar phenomena, likely play an important role in transient events such as flares. Quasi-periodic pulsations (QPPs) flare emissions may be manifestation of oscillatory reconnection, but the underlying mechanisms remain uncertain. In this paper, we present 2D magnetohydrodynamic (MHD) simulations two current-carrying magnetic flux ropes with out-of-plane field undergoing which merge into single rope....